The disclosure of Japanese Patent Application No. 2000-361330 filed on Nov. 28, 2000 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
1. Field of the Invention
The invention relates to a conductive plate, for example, a separator for a fuel cell, which employs fuel gas and oxidant gas as reactive gas.
2. Description of the Related Art
The separator for a fuel cell which employs fuel gas and oxidant gas as reactive gas is provide with a substrate for forming a reactive chamber of the fuel cell and a plurality of protrusions implanted in the substrate such that they protrude from a single side or both sides of the substrate so as to make contact with electrodes of the fuel cell. A plurality of solid electrolyte films and a plurality of positive/negative electrodes are laminated in a plurality of layers so as to form the fuel cell. Because the separator is required to have an excellent conductivity, it is produced for general use by machining a carbon block into a flat substrate having a plurality of protrusions.
Therefore, this type of the separator is expensive, thick and heavy. Because the separator is produced by laminating a plurality of the solid electrolyte films and a plurality of the positive/negative electrodes into a plurality of layers, the fuel cell cannot help being expensive, large and heavy. These problems are a major reason which prevents widespread use of this type of fuel cells. Thus, there has been a demand for this type of the separator, which is also cheap, thin and lightweight and, for example, Japanese Patent Application Laid-Open No. 5-74469 has already disclosed a separator which addresses these problems.
In the separator proposed in that laid-open, a plurality of carbon rods are implanted in a sheet-like molded body made of synthetic resin and respective carbon rods are formed integrally with the sheet-like molded body when that sheet-like molded body is formed.
Meanwhile, in the separator proposed in the above-described publication, the respective carbon rods are implanted integrally with the sheet-like molded body. In this implantation condition, for the respective carbon rods to be supported by the sheet-like molded body in air-tightness without gas leakage, that sheet-like molded body needs to be formed in a sufficiently large thickness. As a result, the separator becomes thick, so that the fuel cell is enlarged in size in the direction of laminating components. Further, upon manufacturing the separator, a plurality of the carbon rods need to be prepared. Because the carbon rods are formed by sintering and molding carbon powder, it takes a high cost to mold a plurality of the carbon rods, so that the price of the carbon rods is reflected upon the separator, thereby increasing the price of the separator.
Accordingly, it is an object of one aspect of the invention to provide a conductive plate, for example, a separator, which is capable of solving the above problems and much thinner, as well as lighter and smaller than the conventional separator and which can be produced at low cost to ensure a cheap price.
To achieve the above object, the conductive plate according to a first aspect of the invention comprises a substrate and a plurality of protrusions implanted in the substrate such that the protrusions protrude from a single side or both sides of the substrate. The substrate has a multiple layered structure in which a single side or both sides of the mesh foundation are covered with resin layers and contains through holes at positions corresponding to each of the protrusions. The respective protrusions are formed by invasion of black lead paint applied on the single side or both sides of the substrate into the respective through holes in the substrate.
Because in the conductive plate according to the first aspect, the substrate is constructed in a multiple layered structure in which a single side or both sides of the mesh foundation are covered with resin layer, the thickness of the substrate can be reduced considerably. Thus, by forming the substrate super thin and lightweight, the conductive plate can be constructed in which the thickness of the substrate that becomes a dead space within the structure of the fuel cell is very small. Consequently, a small fuel cell can be constructed in the direction of laminating the respective components and a large-scale reduction of the weight can be achieved.
According to the manufacturing method of the conductive plate according to a second aspect of the invention, a substrate is formed by covering the mesh foundation with a resin layer, the resin layer being formed by coating a single side or both sides of the mesh foundation with resin or impregnating the mesh foundation with resin and having the through holes at predetermined positions. Then, the black lead paint is applied to one face or both sides of the substrate so as to form protrusions at positions corresponding to the through holes. Next, the thus formed protrusions are hardened.
In the first and second aspects of the invention, the conductive plate may be a separator for a fuel cell.